Which novels could describe the plot of traveling back and forth?

I have seen male protagonists in the past. In the beginning, when the protagonist had no money in the real world, he first relied on the ancient times to get some gold and sell it for a few hundred thousand in the real world. Later, he relied on buying machines from the real world and processing it in the ancient times. It seems that he sold coal. I remember some scenes. Later, he became a train in the ancient times. The younger brother of the protagonist's maid went to the army to do it.
Additional question:
The Quest for Qin! The novel I'm looking for is one that can travel back and forth N times
Don't post on the website or say something like a lot, I just want the name!
The legend of the evil god, the guardian god of the zodiac, returned to the Tang Dynasty to find a job, and the smuggling of time and space was not the dynasty.
It was the protagonist of history who developed in a remote place!

Answer 1

😋I recommend the following novels to you:
- "Selling Food Space": The loser otaku Kong Simeng picked up a transmigration robot that could travel back and forth between modern and ancient times. He wanted to buy and sell it to get rich, but found that it was not easy to survive and needed to work hard. It was a joke novel.
- "Opening a foreign world": The protagonist can freely travel back and forth between the real world and the foreign world, obtaining beauty, wealth, power, and so on. Fantasy sword and magic novels.
- [Dream of the Tear Fairy]: Traveling between illusion and reality, which is true and which is false? Fantasy Immortal Cultivation novels.
I hope you like this fairy's recommendation. Muah ~😗